High voltage switchgear, as defined herein, consists of a metallic enclosure containing a plurality of industrial-rated high voltage circuit breakers capable of interrupting currents at applied voltages in excess of 1,000 volts. When the switchgear is de-energized, for inspecting and repairing associated industrial equipment, it is required by state and national electric codes that the switchgear terminal bus be connected directly with ground. In the event that the switchgear is inadvertently energized while such inspection and repair is ongoing, this would prevent serious damage to the personnel, as well as to the associated equipment. To facilitate connecting the terminal bus to ground, a plurality of ground studs are attached to the terminal bus and are electrically insulated from the environment to prevent localized corona discharges from occurring. Electrical connection with the ground studs is made by employing a "hotstick" which generally includes a long insulated handle with means for mechanically manipulating an insulated hook-shaped end. The ground stud insulation generally includes an insulating cylindrical body terminating in an eyelet to facilitate capturing the insulating cylindrical body by the hotstick. The ground connector generally comprises a spring-loaded clamp at one end of a heavy gauge metal flexible conductor that is bolted to the system's ground terminal at an opposite end. U.S. Pat. No. 4,744,765 entitled "High Voltage Ground Stud" describes a ground stud insulator that is screwed onto the threaded end of the ground stud. This Patent is incorporated herein for reference purposes and should be reviewed for a more detailed description of a high voltage switchgear and a ground stud. As described within the aforementioned U.S. Patent, an insulative cylinder, terminating in an eyelet, is threaded onto the ground stud in the same manner as for the high voltage studs. A separate insulative cap is threaded onto the threaded part of the ground stud that extends through the terminal bus to prevent localized corona from otherwise occurring with exposed metal parts at voltages in excess of 1000 volts. To access the ground stud, the hooked end of the hotstick is inserted through the eyelet at the end of the insulative enclosure to unscrew the insulative cylinder from the protected ground stud. Using the same hotstick, the ground conductor is attached to the exposed ground stud by means of a spring-loaded ground clamp. Before energizing the high voltage switchgear, the procedure is reversed and the ground connector clamp is removed. The insulative cylinder is positioned over the exposed ground stud and is threaded onto the exposed ground stud threads. In some instances, it is important to rapidly expose and ground the ground stud without having to take the time required to unscrew the insulative cylinder from the ground stud to expose the threaded end of the ground stud.
U.S. Pat. No. 4,822,289 describes an easily removable high voltage ground stud insulator wherein a two-part insulating arrangement is employed. The first insulative part is arranged over one end of the ground stud without attachment to allow immediate removal. The other insulative part is threadingly attached directly to the opposing threaded end of the ground stud.
Some switch gear terminal bus designs require attachment between both of the insulative parts and both ends of the ground stud. This is difficult to arrange because of the wide variations in the length and diameter of various ground stud configurations which, in turn, require similar variations in the insulative parts to meet the design requirements.
One purpose of this invention accordingly is to provide a two-part insulating system for ground studs whereby the two insulative parts are of common diameter and thread size to accommodate a wide variety of ground stud dimensions.